Generally, a vehicle includes an air-bag device for protecting a vehicle driver and passengers from receiving physical shock caused by a vehicle crash or a head-on collision between vehicles. The above-mentioned air-bag devices installed in vehicles as optional devices have been widely used throughout the world. Specifically, air-bag devices for vehicle drivers have been required in most vehicles in recent times, and air-bag device for protecting passengers from danger or other air-bag devices for protecting vehicle drivers or passengers from a lateral collision have also been widely used throughout the world.
If vehicles collide with each other, a conventional determines the presence or absence of the vehicle collision. Upon a vehicle collision, the air-bag device is rapidly operated by an electric signal generated by the vehicle collision. For example, when the air-bag device is operated by the vehicle collision on the condition that a vehicle driver traveling in his or her vehicle has moved a vehicle seat to the front most area according to a body type of the vehicle driver, a distance between the vehicle driver and the air-bag device becomes short, such that the vehicle driver may be injured or suffocate d by impact caused by the air-bag device's operation.
In order to solve the above-mentioned problems, a variety of devices have recently been proposed, for example, devices for detecting the location of a vehicle seat and selectively operating the air-bag device according to the detected location. As well known to those skilled in the art, a representative scheme for detecting the vehicle seat location in the above-mentioned devices includes a noncontact-type sensor, for example, a magnet, a hall sensor, an ultrasonic sensor, etc. In addition, another scheme for detecting the vehicle seat moving along a rail using a contact-type sensor has also been recently proposed. Specifically, the noncontact-type sensors based on the magnet and the hall sensor have been more widely used than other sensors.
Two-pin hall sensors and three-pin hall sensors have been widely used for detecting the vehicle seat location. It should be noted that the two-pin hall sensor and the three-pin hall sensor have the following disadvantages.
Firstly, a representative example of the two-pin hall sensor is “TLE4976L” manufactured by Infineon Company. In the TLE4976L sensor, a first pin contained in the two-pin hall sensor serves as a power-supply pin, and a second pin contained in the same serves as a ground pin. One pin of the two pins is not internally connected, such that the exemplary hall sensor may be generally referred to as a two-pin hall sensor.
The above-mentioned two-pin hall sensor is connected to an air-bag controller (ACU) for providing a supply-voltage pulse. The above-mentioned ACU controls the opening of an air-bag according to a variation in a current level ISlow and IShigh applied to the two-pin hall sensor. If a target (may be a magnet) is located in a hysteresis period as shown in FIG. 1, a current level applied to the two-pin hall sensor does not maintain a predetermined level (i.e., a high or low level), and moves between the high level IShigh and the low level ISlow. For example, the current level is transitioned from the high level IShigh to the low level ISlow or from the low level ISlow to the high level IShigh, because a power-supply signal is not continuously applied to the ACU. In this case, the ACU determines the presence or absence of an erroneous operation of the hall sensor, such that a warning lamp is switched on or off according to the determined result.
Therefore, the vehicle driver wrongly determines the presence of an erroneous operation of an air-bag system although there is no error in the air-bag system, such that an after-sale service is unnecessarily required.
In order to solve the above-mentioned problems, the three-pin hall sensors have been used. A representative example of the three-pin hall sensor is “TLE4906L” manufactured by Infineon Company. In the TLE4906L sensor, a first pin contained in the three-pin hall sensor serves as a power-supply pin, a second pin serves as a ground pin, and a third pin serves as an output pin configured in the form of an open-collector. A peripheral circuit diagram of the hall sensor for detecting a vehicle seat location using the three-pin hall sensor is depicted in FIG. 2.
As shown in FIG. 2, the three-pin hall sensor 10 receives a power-supply signal via a power-supply pin (Vs), and controls one end of the CPU to be grounded according to the target detection result.
Therefore, the ACU equipped with the three-pin hall sensor controls the opening of an air-bag according to a variation in a current level applied to the three-pin hall sensor. Although unexpected errors occur in the three-pin hall sensor by external impact and electrical impact, a closed loop (P1) caused by resistors R1 and R2 is formed, such that the ACU does not wrongly indicate a malfunction or error of the hall sensor. In other words, since the three-pin hall sensor has no self-diagnosis function, the three-pin hall sensor is unable to detect its malfunction or error under the condition that the malfunction or error has occurred in the three-pin hall sensor, such that the air-bag cannot be controlled by the three-pin hall sensor.
In the meantime, a typical hall sensor module is bolt-connected to a guide track which moves forward and backward with a vehicle seat, such that it has difficulty in the replacement and installation of the above-mentioned typical hall sensor.